This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. he purpose of the project, which is ongoing, is to study 48 pairs of monozygotic twins using a longitudinal cotwin-control design to assess effects of alcohol and drug use on brain structure and function. The project uses a comprehensive and complementary battery of neuropsychological, psychophysiological and MRI assessment. MRI imaging includes high-resolution structural imaging for morphometric analyses and whole-brain functional imaging during performance of a task shown to be sensitive to reward-sensitive neural areas.